An ambassador from Asia was told that, if he voted in favor of the plan, his country’s sailors would no longer be allowed to disembark at American ports. Caribbean diplomats were told that they could be blacklisted from entering the United States. And Marco Rubio, the secretary of state, personally called officials in several countries to threaten financial penalties and other punishments if they continued to support the agreement to cut ship pollution.

These and other threats, including tariffs, sanctions and the revocation of diplomats’ U.S. visas, effectively killed the deal, according to the nine American, European and developing-nation diplomats directly involved in the negotiations. They spoke on the condition of anonymity out of fear of retribution from the Trump administration